A Mathematical Method for Eliminating Spin Losses in Toroidal Traction Drives

Abstract

The efficiency of the original Toroidal continuously variable transmission (CVT) is limited due to the spin losses caused by the different speed distribution in the contact area. To overcome this drawback, this paper replaces the original working surface with a new surface derived from a differential equation and proposes a novel Logarithmic CVT. Equations and ranges of the transmission ratio range, half-cone-angle, and conformity ratio, which are essential geometrical parameters of the Logarithmic CVT, are derived. A set of geometrical parameters is further recommended. With such geometrical parameters, the transmission ratio range of the Logarithmic CVT is as wide as that of the Half-Toroidal CVT. The two types of CVTs are compared with each other in terms of efficiency based on a widely accepted computational model. The results show that efficiency of the Logarithmic CVT is higher than that of Half-Toroidal CVT except for some particular situations because of the thrust bearing losses.

Design principles and traction performance of a novel zero-spin rolling conical traction continuously variable transmission

“…A large number of studies [9][10][11][12] have shown that spin losses affect the traction performance of t-CVT significantly. Therefore, decreasing the spin losses can improve the reliability and fatigue life [13] , increase the power density and torque capacity [7,14] , and greatly improve the traction efficiency of traction CVT [15][16][17] .…”

“…Then, a novel double roller Full-Toroidal CVT(FT-CVT) was designed by Novellis et al [17] , and this type of CVT can also significantly decrease the spin losses. However, the most representative research was the zero-spin design methodology developed by Li et al [15,16] . The core idea of this methodology was that the original working surface of drive or driven components were redesigned to satisfy the zero-spin condition mentioned above.…”

Adaptive loading ball traction drive reducer: modeling and efficiency performance

“…It should be limited or eliminated in design due to its energy loss. Although the generatrix of the traction component has been redesigned to replace the circular generatrix and realizing zero-spinning theoretically (Li et al, 2019;Li et al, 2015aLi et al, , 2015b, it is also intractable for the new generatrix to be expressed by primary functions and manufactured. Therefore, the usual mean to limit the spin loss for improving efficiency is reducing the contact angle, which is also adapted in the proposed structure.…”

Design Principles and Traction Performance of a Novel Zero-spin Rolling Conical Traction Continuously Variable Transmission

“…A large number of studies [9][10][11][12] have shown that spin losses affect the traction performance of t-CVT significantly. Therefore, decreasing the spin losses can improve the reliability and fatigue life [13] , increase the power density and torque capacity [7,14] , and greatly improve the traction efficiency of traction CVT [15][16][17] .…”